Effect of 3'-methyl-4-dimethylaminoazobenzene in the induction of malignant transformation and of 8-azaguanine-resistant mutations and chromosomal aberrations in a diploid clone derived from normal rat liver cells in culture.

The effect of 3' methyl-4-dimethylaminoazobenzene (3'-Me-DAB) in the induction of malignant transformation and of 8-azaguanine-resistant mutations and chromosomal aberrations was studied in a diploid strain derived from normal rat liver cells. The cells were malignantly transformed by treatment with 3'-Me-DAB 1.7 micrograms/ml for 130 to 221 d or 1.7 micrograms/ml for 53 d followed by 24.9 micrograms/ml for 27 to 77 d. The untreated control cells did not transform spontaneously until the 232nd d in culture. Some properties of the 3'-Me-DAB-treated cells were compared to those of untreated control cells but no reliable marker for predicting the tumorigenic potential of the cells was found. The single addition of 3'-Me-DAB caused little induction of 8-azaguanine-resistant mutations and chromosomal aberrations to the cells. However, mutations and chromosomal aberrations were significantly induced by N-acetoxy-4-methylaminoazobenzene, an active metabolite of 4-dimethylaminoazobenzene or 3'-Me-DAB in the presence of liver microsomes.